A large number of different types of foods are fed to fish such as goldfish, mariculture fish or tropical fish both in a natural environment and a controlled environment such as in aquariums or special tanks or ponds. Usually, the most preferred fish foods are the naturally occuring water animals such as Daphnia pulex, Artemia salinas (brine shrimp), mosquito larvae, Tubifex worms and Cyclops. Such natural foods are best for optimum fish growth and condition, and in some species of fish are even essential for breeding.
However, these natural foods are usually quite expensive to obtain, may have a short lifetime, and are difficult to keep. In addition, introduction of these types of foods carries a hazard of potentially introducing water borne diseases into the aquarium. The availability of this type of food is largely seasonal, and these foods may not even be available during the winter season.
As a result, many types of processed or prepared fish foods have been introduced commercially, including both preserved natural foods or specially prepared foods.
One type of processed fish food is the baked and ground cake type foods. Such foods are among the oldest and most common types of fish foods, and are frequently used for commercial fish raising of many types and species, including trout, catfish, tropical fish, goldfish and shrimp.
Such cake type fish foods are inexpensive and easy to store. However this type of food tends to foul the water, and usually does not produce good color on ornamental fish. Often, this type of food will not bring fish of any type to a breeding condition.
Flaked foods are another type of fish food which are much easier to produce in high quality than the baked and ground cake type, as the processing does not heat the food to the high temperatures of baking, nor is the cooking period as long. This type product has better vitamin content than the baked food and is more palatable to the fish, since baking destroys the "raw taste" which fish seem to prefer.
However, flaked foods require much higher processing costs and high energy consumption for production, resulting in significantly higher product cost compared to the baked products. Furthermore, due to the finer milling requirements in preparation, the flaked products are quite bulky and hard to store in flake form, as the flakes damage to powder very easily.
An advance over the handling of live foods is achieved through the freezing of such live foods. Such frozen products are easier to handle than live foods, but still are very energy intensive in production operations. High energy costs are needed to process the food by the manufacturer, and such costs continue for the transportation and the storage of such products. Thawing of the product at any stage prior to use will destroy any such products in minutes. Moreover, some frozen foods such as fish and shrimp lose useful food values within a few months due to freezing, as enzyme action causes deterioration by reducing the protein and vitamin content.
An advance over freezing of such foods has taken place through the development of freeze drying techniques. Freeze dried products are much easier to handle and store, and these products do not deteriorate as fast as frozen fish food. Indeed, freeze dried products may be stored for years without appreciable deterioration. However, freeze drying, like freezing, is very energy intensive, and thus quite expensive for commercial production of fish food. The high cost of freeze drying often prevents the use of this technique for commercial operations.
The oldest type of preservation of fish food is by air drying of the food. Such preservation requires almost no machinery or energy at any stage of the processing. However, the commercial viability of such a process and product is quite poor, since the air drying reduces the food value by causing rancidity of the fat in the process. Almost all palatability, vitamin content, color, odor, freshness and live texture is lost in such processing, and the resulting fish food is poorly accepted by all fish.
A need, therefore, exists for a fish food product which is acceptable and nutritional to fish, which is of low manufacturing and processing costs, which may be stored for extended periods of time without deterioration, and which may be easily packaged and handled.